djvup

[Content by Gemini 2.5]

Technical Breakdown: DJVUP Ransomware (STOP/Djvu Family)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Encrypted files are appended “.djvup” in lower-case, producing filenames such as:
  • invoice_2024Q2.docx → invoice_2024Q2.docx.djvup
  • FamilyPhotos.rar → FamilyPhotos.rar.djvup
  • Renaming Convention:
    The malware prepends a random 5-9 character ID (“abc12”, “nyx08”, …) to the extension only in the README.txt ransom note, not on disk. Disk entry is strictly: original name + “.djvup”.

2. Detection & Outbreak Timeline

  • Approximate Start Date: First public sightings reported late February 2024 (Emsisoft Telemetry, ID-Ransomware uploads).
    A second, slightly updated wave began mid-May 2024, matching campaigns that push fake Windows-11 ISOs on BitTorrent.

3. Primary Attack Vectors

| Vector | Details | Mitigation Short-Form |
|—|—|—|
| Pirated-Software Bundles | Malicious cracks/keygens for Photoshop, Vmware Workstation-16, etc. | Block untrusted downloads, enforce EDR quarantine on new EXE |
| Malvertising Lures | “Crack[.]onl” type of redirect chains serving FakeUpdate (SocGholish/JavaScript downloaders). | Block malicious ads via DNS filtering (Quad9/1.1.1.2) |
| Exploit for CVE-2023-36884 | Uses one-line PowerShell to fetch LOB.dll, leading to DJVUP dropper. Patch July 2023 Office update. | Roll out KB5022368 / M365 version 2306 build |
| USB worms | Rarely: Autorun.inf drop in shared USB drives. | Disable AutoRun via GPO, granular USB-control policies |
| RDP brute-force remnant | Secondary installer attempt if SYSTEM already breached. | Strong passwords, RDS-gateway + 2-FA, lockout policy |

Remediation & Recovery Strategies:

1. Prevention

  • Patch CVE-2023-36884 and August-2024 cumulative Windows updates.
  • Deploy EDR rules watching for SHA256 4f4df91802bc9f9e9182e841947f0fc46bcccb9a25e6dc872327793c17abfa97 (current DJVUP dropper).
  • Disable Windows Script Host & PowerShell v2 endpoints unless strictly required.
  • Segment networks: use AppLocker to block executables launched from %USERPROFILE%\Downloads.
  • Standardize on least-privilege accounts; never surf & download under local-admin.

2. Removal

  1. Isolate immediately: Pull network cable / disable Wi-Fi.
  2. Boot Hiren/WinRE → run offline AV scans (Kaspersky Rescue or Microsoft Defender Offline) to clear:
    %TEMP%\[random]\install.exe, C:\Windows\System32\spool\drivers\color\helper.dll.
  3. Registry cleanup: Remove keys under HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run that contain “syshelper.exe”, “winlogon.exe” (impersonated path).
  4. Service termination: In Safe Mode, stop & delete service Windows Accelerator Service (disguised as WerFault.exe inside %APPDATA%\Roaming\Microsoft\).
  5. Verify persistence: Use Autoruns or Glary Startup-Manager to ensure no scheduled task WinRing0_1_1_0 remains.
  6. Reboot normally → update OS, AV signatures, then scan again.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – CURRENT variant (May-2024): Encryption uses online key unique per machine; general decryptor NOT available.
    – Exception: if the malware fails to reach its C2, it falls back to an offline key (fixed “dkYORKx轲6?” for the Feb-2024 wave).
    – Tool: Emsisoft STOP/Djvu Decryptor v1.0.0.24 can restore data encrypted by offline keys. Download from: https://www.emsisoft.com/ransomware-decryption-tools/stop-djvu.
    – Cloud/Snap-In Recycle Bin: Leverage OneDrive/SharePoint file history and Windows shadow copies (vssadmin list shadows) before the malware deletes them.
    – Quick Patch/Fix: Apply the registry setting HKLM\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotToSnapshotto forcibly keep VSS alive when Dropbox, OneDrive & 7-Zip are running.

4. Other Critical Information

  • Fast encryption in multi-thread mode (32 worker threads on CPU ≥4 cores). Only files ≤150 MB are encrypted completely; files >150 MB are partially overwritten – never overwrite or chmod files before attempting recovery (chunks remain restorable by carvers like PhotoRec).
  • Shred-Tool Chain: After encryption it launches cipher /w: giving illusion of secure wipe—pure smoke: only creates zeroed-fill dummy files. Recovery bytes still reside on disk until overwritten naturally.
  • Notable socio-impact: DJVUP variants are heavily promoted on “crack[.]so” domains which enjoy Alexa top-10K traffic – every new release surfaces hundreds of gigabytes of lost personal archives worldwide within a single weekend.
  • Direct-communication channel: Newest notes push victims to “support@djvu-support[.]io” (Telegram drop + TOX bot user 756DBFACC10..), using internationalized cloudsoft fonts so OCR scanners skip email for automated feeds.

Bottom-line stack for your environment:
Patch → EDR rules > Pirated warez block > 3-2-1 backup on immutable cloud → keep the Emsisoft/Avast decryptor at the ready.